Method of uniting optical fibers

ABSTRACT

After a number of optical fibers are inserted into a tubular member of a shape memory alloy, the tubular member is returned to its memorized shape by heating to reduce a cross-sectional area of a reception space of the tubular member, thereby uniting the optical fibers received in the tubular member. In a modified form of the invention, a number of optical fibers are inserted into a reception space between two tubular members at least one of which is made of a shape memory alloy, and then the one tubular member is heated to be returned to its memorized shape to reduce a cross-sectional area of the reception space between the two tubular members, thereby uniting the optical fibers. In another modified form of the invention, a number of optical fibers are inserted into a reception space formed between an inner periphery of a tubular member and a partition plate of a shape memory alloy, and then the partition plate is heated to be returned to its memorized shape to reduce a cross-sectional area of the reception space, thereby uniting the optical fibers.

BACKGROUND OF THE INVENTION

This invention relates to a method of uniting a number of optical fibersinto a bundle.

An optical fiber bundle has been widely used for transmittingillumination light in an endoscope. The optical fiber bundle is obtainedby uniting or Joining at least opposites ends of a number of opticalfibers. Generally, tubular members have conventionally been used forthis uniting operation. More specifically, the end portions of a numberof optical fibers to which an adhesive has been applied are insertedinto the tubular members, and the optical fibers are united togetherupon solidification of the adhesive. It is preferred that as manyoptical fibers as possible be inserted into the tubular member so as toincrease the density of filling of the optical fibers. In the abovemethod, however, when trying to insert as many optical fibers aspossible into the tubular member, the optical fibers are rubbed by theinner surface of the tubular member, and are damaged. Therefore, toincrease the density of filling of the optical fibers has been limited.

Japanese Laid-Open Utility Model Application No. 59-43903 discloses amethod of uniting optical fibers together, in which a number of opticalfibers are first inserted into a tubular member of a circularcross-section, and then a wedge member is inserted into the tubularmember, thereby increasing the density of filling of the optical fibers.However, when the wedge member is inserted into the tubular member, thewedge member rubs the optical fibers, and therefore may damage them.

In some cases, optical fibers in a bent condition are united together.For example, Japanese Laid-Open Patent Application No. 59-34239 shows inFIG. 5 a front end structure of an endoscope of a side-viewing type. Endportions of optical fibers are bent generally right-angularly orperpendicularly, and in this condition they are united together by auniting member. Although not described in detail in this publication,this uniting member is composed of two halves, and a pair of curvedgrooves are formed respectively in opposed surfaces of the two halves.The optical fibers are received in these grooves, and the two halves areconnected together, with the two grooves mated together, thereby unitingthe optical fibers. In this uniting method, the density of filling ofthe optical fiber is low, and the uniting operation is quite cumbersome.

A pamphlet "KSM alloy", published by Kanto Tokushuko K. K, discloses ajoint for connecting two pipes together. This joint has a tubular shape,and is made of a shape memory alloy. Opposed ends of the two pipes areinserted respectively into the opposite end portions of the Joint, andthen heat is applied to the joint to return it to its memorizedconfiguration, that is, a smaller diameter, thereby connecting the twopipes together.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a method of uniting opticalfibers with a high filling density without damaging the optical fibers.

According to one aspect of the present invention, there is provided amethod of uniting a number of optical fibers comprising the steps of:

(a) processing a tubular member of a shape memory alloy with a receptionspace in such a manner that the cross-sectional area of the receptionspace is larger than that in a memorized shape of the tubular member;

(b) inserting a number of optical fibers into the tubular member; and

(c) subsequently heating the tubular member to return the same to itsmemorized shape to reduce the cross-sectional area of the receptionspace, thereby uniting the optical fibers received In the tubularmember.

According to another aspect of the invention, there is provided a methodof uniting a number of optical fibers comprising the steps of:

(a) inserting an inner tubular member and a number of optical fibersinto an outer tubular member, the outer and inner tubular membersforming a reception space therebetween in which the optical fibers arereceived, and at least one of the outer and inner tubular member beingmade of a shape memory alloy; and

(b) subsequently heating the one tubular member to return the same intoits memorized shape to reduce a cross-sectional area of the receptionspace, thereby uniting the optical fibers received in the receptionspace.

According to a further aspect of the invention, there is provided amethod of uniting a number of optical fibers comprising the steps of:

(a) inserting a partition plate and a number of optical fibers into atubular member, so that an internal space of the tubular member isdivided into two sections, one of the two sections serving as areception space for receiving the optical fibers, and the partitionplate being made of a shape memory alloy; and

(b) subsequently heating the partition plate to return the same to itsmemorized shape to reduce a cross-sectional area of the reception space,thereby uniting the optical fibers received in the reception space.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a tubular member of a shape memory alloyexpanded in diameter;

FIG. 2 is a longitudinal cross-sectional view of the tubular member intowhich end portions of a number of optical fibers are inserted;

FIG. 3 is a longitudinal cross-sectional view, showing a condition intubular member of FIG. 2 is reduced in diameter by heating, therebyuniting the optical fibers together;

FIG. 4 is a longitudinal cross-sectional view, showing a condition inwhich the end portions of the united optical fibers of FIG. 3 are cutoff;

FIG. 5 is a perspective view, showing an endoscope, incorporating theoptical fibers united at their opposite ends, and a light source device;

FIG. 6 is a vertical cross-sectional view showing the relation between aconnector of the endoscope containing one end portions of the unitedoptical fibers and a light source;

FIG. 7 is a longitudinal cross-sectional view of a tip member of theendoscope containing the other end portions of the united opticalfibers;

FIG. 8 is a longitudinal cross-sectional view, showing a tubular memberwhich is used in a modified optical fiber uniting method and has not yetbeen heated;

FIG. 9 is a longitudinal cross-sectional view of a connector containingone end portions of optical fibers united together by the method of FIG.8;

FIG. 10 is a longitudinal cross-sectional view, showing a tubular memberwhich is used in another modified optical fiber uniting method and hasnot yet been heated;

FIG. 11 is a longitudinal cross-sectional view of a connector containingone end portions of optical fibers united together by the method of FIG.10;

FIGS. 12 to 16 are perspective views respectively showing modifiedtubular members of various shapes used for uniting optical fibers;

FIG. 17 is a longitudinal cross-sectional view, showing a tubular memberwhich is used in a further modified optical fiber uniting method and hasnot yet been heated;

FIG. 18 is a longitudinal cross-sectional view showing a condition inwhich the tubular member of FIG. 17 is reduced in diameter by heating tounit optical fibers;

FIG. 19 is a longitudinal cross-sectional view showing a condition inwhich the end portions of the united optical fibers of FIG. 18 are cutoff;

FIG. 20 is a longitudinal cross-sectional view, showing a tubular memberwhich is used in a further modified optical fiber uniting method and hasnot yet been heated;

FIG. 21 is a longitudinal cross-sectional view, showing a tip membercontaining end portions of optical fibers united by the method of FIG.20;

FIG. 22 is a longitudinal cross-sectional view, showing a tubular memberwhich is used in a further modified optical fiber uniting method and hasnot yet been heated;

FIG. 23 is a longitudinal cross-sectional view of a body containingoptical fibers united by the method of FIG. 22;

FIG. 24 is a perspective view of two tubular members used for unitingoptical fibers;

FIG. 25 is a longitudinal cross-sectional view showing a tip membercontaining the end portions of the optical fibers united by the use ofthe two tubular members of FIG. 24;

FIG. 26 is a perspective view of modified two tubular members similar tothose of FIG. 24;

FIG. 27 is a transverse cross-sectional view of a tubular member and apartition member used in a further modified optical fiber unitingmethod, showing a condition in which optical fibers have not yet beenunited;

FIG. 28 is a transverse cross-sectional view showing a condition inwhich the optical fibers are united together by heating the partitionplate of FIG. 27; and

FIG. 29 is a longitudinal cross-sectional view of a tip membercontaining the end portions of the optical fibers united by the methodof FIG. 28.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Methods of the present invention will now be described with reference tothe drawings. First, a first embodiment of the invention will bedescribed with reference to FIGS. 1 to 4. As shown in FIG. 1, a tubularmember 10 is prepared. This tubular member 10 is made of a shape memoryalloy. The tubular member 10 is processed with respect to its memory ata temperature higher than an ordinary temperature (room temperature),and its memorized shape is a cylinder having an inner diameter d₁, asshown in FIGS. 3 and 4. The tubular member 10 is expanded in diameter atthe ordinary temperature into a cylinder having an inner diameter d₂ (d₂>d₁), as shown in FIGS. 1 and 2. The internal space or interior of thetubular member 10 serves as a reception space 11. The cross-sectionalarea of the reception space 11 is uniform throughout the length of thetubular member 10. A through hole 12 is formed through the peripheralwall of the tubular member 10.

On the other hand, as shown in FIG. 2, there are prepared a maximumnumber (for example, several thousands to several tens of thousands) ofoptical fibers 20 which can be inserted into the tubular member 10,having the inner diameter d₂, without damage. One ends of these opticalfibers 20 are disposed generally in a common plane, and in thiscondition an adhesive is applied to almost all of the optical fibers 20over a predetermined distance (indicated by L in FIG. 2) from the oneends thereof.

Then, as shown in FIG. 2, a number of optical fibers 20 mentioned aboveare inserted into the reception space 11 of the tubular member 10, andone ends of the optical fibers 20 are projected from one end of thetubular member 10. Since the diameter of the tubular member 10 is large,the optical fibers 20 can be easily inserted into the tubular member 10without damage. The tubular member 10 is disposed on those portions ofthe optical fibers 20 to which the adhesive has been applied.

Then, as shown in FIG. 3, the tubular member 10 is heated to be returnedto its memorized shape, that is, into the cylindrical shape having theinner diameter d₁. As a result, the optical fibers 20 are unitedtogether by the tubular member 10. Thus, even though the inner diameterd₁ of the tubular member 10 is small, the number of optical fibers 20 tobe united together can be increased, so that the density of filling ofthe optical fibers 20 can be increased.

The adhesive is cured or set by the above heating. The cured adhesiveprevents the optical fibers 20 from being withdrawn from the tubularmember 10 after the optical fibers 20 are united together. The adhesivefills in gaps between the optical fibers 20 to thereby prevent theintrusion of water.

When the tubular member 10 is reduced or contracted in diameter byheating, the adhesive leaks from the through hole 12 in the tubularmember 10. Therefore, the amount of flow of the adhesive along theoptical fibers 20 can be reduced. As a result, straight portions of theoptical fibers 20 which are unable to be bent after the curing of theadhesive can be shortened.

Then, as shown in FIG. 4, the end portions of the united optical fibers20 projected from the end of the tubular member 10 are cut off, so thatthe cut ends of the optical fibers 20 lie substantially flush with theend of the tubular member 10. Then, the end faces of the optical fibers20 are polished. The other ends of the optical fibers 20 are unitedtogether by the use of another tubular member 10' similar to the tubularmember 10 in a manner described above. An optical fiber bundle 25,obtained by uniting both ends of the optical fibers by the respectivetubular members 10 and 10', is incorporated, for example, into anendoscope 50 (FIG. 5) for transmitting illumination light.

The endoscope 50 comprises a body 51, a flexible insertion portion 52extending from the body 51, a bending portion 53 extending from a frontend of the insertion portion 52, a rigid tip member 54 provided at afront end of the bending portion 53, a light guide cable 55 extendingfrom the body 51, and a connector 56 mounted on a distal end of thelight guide cable 55. A manipulation member 57 is mounted on the body51, and by operating this manipulation member 57, the bending portion 53is bent in a remotely-controlled manner. An ocular portion 58 is furtherprovided on the body 51.

As shown in FIG. 6, one end portion of the optical fiber bundle 25inserted into the connector 56 of a tubular shape, and is fixed to thisconnector 56 by a screw (not shown) which is threaded through theperipheral wall of the connector 56, and is firmly held at its distalend against the outer peripheral surface of the tubular member 10. Theoptical fiber bundle 25 passes sequentially through the light guidecable 55, the body 51, the insertion portion 52 and the bending portion53, and is inserted into and fixed to the tip member 54 at the other endportion thereof, as shown in FIG. 7. More specifically, the tubularmember 10' of the optical fiber bundle 25 is inserted into and fixed toa retainer tube 26. A flat pane 27 of glass, serving as an illuminationwindow, is fitted in the front end of the retainer tube 26. The retainertube 26 is fitted in and fixed to a through hole 54a formed through thetip member 54.

An image transmission optical system 30 shown in FIG. 7 is providedbetween the ocular portion 58 and the tip member 54. The imagetransmission optical system 30 comprises an optical fiber bundle 31. Theoptical fiber bundle 31 comprises a number of optical fibers 32 unitedat their opposite ends by tubular members 33. One end portion of theoptical fiber bundle 31, as well as a flat pane 37 of glass (whichserves as an inspection window) and an objective lens 38, is fitted inand fixed to a retainer tube 36. This retainer tube 36 is inserted intoand fixed to a through hole 54b of the tip member 54. The other endportion of the optical fiber bundle 31 is fixed, together with an ocularlens, to the ocular portion 58.

As shown in FIGS. 5 and 6, the connector 56 of the endoscope 50 isconnected to a light source device 60. The light source device 60comprises a concave mirror 61 within a housing, and a lamp 62 whichserves as a light source and mounted on the concave mirror 61.Illumination light from the lamp 62 is reflected by the concave mirror61 to converge, and is incident on one end faces of the optical fibers20 supported by the connector 56. This incident light passes through theoptical fibers 20, and is applied to a body cavity via the illuminationwindow 27. An image of an inner wall of the body cavity can be observedfrom the ocular portion 58 via the image transmission optical system 30.

In the connector 56, since the density of filling of the optical fibers20 in the tubular member 10 is high, the connector 56 can efficientlyreceive the illumination light from the lamp 62. Also, in the tip member54, since the density of filling of the optical fibers 20 in the tubularmember 10' is high, a large amount of light can be applied from thetubular member 10' having a relatively small transverse cross-sectionalarea.

Other embodiments of the present invention will be described below. Inthese embodiments, those portions corresponding respectively to those ofpreceding embodiments are designated by identical reference numerals,respectively, and detailed explanation thereof will be omitted. In allof the embodiments described hereinafter, an adhesive is used foruniting optical fibers together.

In the embodiment shown in FIGS. 8 and 9, a tubular member 10A isuniform in thickness throughout the length thereof, and an innerdiameter of the tubular member 10A, as well as its outer diameter, isdecreasing progressively toward one end of the tubular member 10A. Areception space 11A of the tubular member 10A has a circular transversecross-section, and is decreasing progressively toward one end thereof.The tubular member 10A is made of a shape memory alloy, and is processedin such a manner that it is larger in diameter than its memorized shape.As shown in FIG. 8, optical fibers 20 are inserted into the receptionspace 11A of the tubular member 10A, and then a core 15A of a conicalshape is inserted into a bundle of optical fibers 20. As a result, theoptical fibers are disposed between the outer peripheral surface of thecore 15A and the inner peripheral surface of the tubular member 10A. Inthe condition shown in FIG. 8, the tubular member 10A is heated to bereturned to its memorized shape having the smaller diameter, so that theoptical fibers 20 are united together. Thereafter, the end portions ofthe optical fibers 20 projected from one end of the tubular member 10Ais cut off, so that the cut ends of the optical fibers 20 liesubstantially flush with the one end of the tubular member 10A. As shownin FIG. 9, the end portions of the thus united optical fibers 20 areinserted into and fixed to a connector 56A of an endoscope. The endportions of the optical fibers 20 flare to the left in FIG. 9, andtherefore the angle between illumination light, which is emitted from alight source to be incident on each optical fiber 20, and the opticalfiber 20 is small, so that the optical fibers 20 can efficiently receivethe illumination light.

In the embodiment shown in FIGS. 10 and 11, a tubular member 10B made ofa shape memory alloy has a cylindrical outer peripheral surface. Areception space 11B of the tubular member 10B has a circular transversecross-section, and is decreasing at its one end portion progressivelytoward one open end of the tubular member 10B. The tubular member 10B isprocessed in such a manner that this open end is larger in diameter thanits memorized shape. A core 15B has a left end portion of a cylindricalshape, and a right end portion of a conical shape. As shown in FIG. 10,optical fibers 20 are disposed between the tubular member 10B and thecore 15B. When the tubular member 10B is heated, the open end of thetubular member 10B is returned to its memorized shape as shown in FIG.11, so that the optical fibers 20 are united together. The end portionsof the thus united optical fibers 20 are inserted into and fixed to aconnector 56B.

FIGS. 12 to 16 respectively show modified tubular members of a shapememory alloy in their respective memorized shapes, which tubular membersare used for uniting optical fibers. The tubular member 10C of FIG. 12has one end portion of a circular transverse cross-section, and theother end portion of an oval transverse cross-section. The tubularmember 10D of FIG. 13 has a cylindrical shape at its one end portion,and is increasing in diameter toward the other end. Each of the tubularmembers 10C and 10D are processed in such a manner that it is larger indiameter than its memorized shape throughout the length thereof. Thetubular member 10E of FIG. 14 includes an outer arcuate portion 10Ea, aninner arcuate portion 10Eb, and a pair of connecting portions 10Ecinterconnecting the outer and inner arcuate portions 10Ea and 10Eb atopposite ends thereof. A reception space 11E of the tubular member 10Ehas a generally C-shape. The tubular member 10E is processed in such amanner that the outer arcuate portion 10Ea is larger in diameter thanits memorized shape. The tubular member 10F of FIG. 15, as well as thetubular member 10G of FIG. 16, has a generally rectangularcross-section. Each of these tubular members 10F and 10G is processed insuch a manner that its reception space 11F, 11G is larger incross-sectional area than that of the memorized shape.

In the embodiment shown in FIGS. 17 to 19, a coil 10H made of a shapememory alloy is used as a tubular member. As shown in FIG. 17, the coil10H is processed in such a manner that it is larger in diameter than itsmemorized shape. A number of optical fibers 20 are inserted into areception space 11H of the tubular member 10H, and one end portions ofthe optical fibers 20 are projected from one end of the tubular member10H. Then, as shown in FIG. 18, the tubular member 10H is heated to bereturned to its memorized shape having the smaller diameter, therebyuniting the optical fibers 20 together. Then, as shown in FIG. 19, theend portions of the optical fibers 20 projected from the tubular member10H are cut off, so that the cut ends of the optical fibers 20 liesubstantially flush with the end of the tubular member 10. Then, the endfaces of the optical fibers 20 are polished.

The optical fibers united by the above tubular members 10C to 10H areused for transmitting illumination light in an endoscope.

The embodiment shown in FIGS. 20 and 21 is directed to a method ofobtaining an optical fiber bundle 25J used in an endoscope of aside-viewing type. As shown in FIG. 21, in its memorized shape, atubular member 10J used in this embodiment has a circular cross-section,and has an axis of an L-shape which is bent generally perpendicularly.As shown in FIG. 20, the tubular member 10J is processed in such amanner that it is larger in diameter and is curved along its axis moregently than its memorized shape. One end portions of a number of opticalfibers 20 are inserted into the tubular member 10J. At this time, thecurvature or bending of the tubular member 10J in the axial direction isgentle, and besides the cross-sectional area of a reception space 11J islarge, and therefore the insertion of the optical fibers 20 is easy.Then, the tubular member 10J is heated to be returned to its memorizedshape, so that the tubular member 10J is reduced in diameter and isbrought into the perpendicularly-bent condition, thereby uniting the oneend portions of the optical fibers 20. Then, the end portions projectedfrom the tubular member 10J are cut off. The other end portions of theoptical fibers 20 are united together in the manner as described in anyone of the above embodiments.

As shown in FIG. 21, one end portion of the thus obtained optical fiberbundle 25J is incorporated into a tip member 54J of the endoscope. Thetip member 54J is composed of two halves having L-shaped grooves intheir opposed surfaces, respectively. The two halves are joined togetherwith the tubular member 10J fitted in the opposed L-shaped grooves,thereby attaching the optical fiber bundle 25J to the tip member 54J.The pair of grooves cooperate with each other to form a through hole54Ja receiving the tubular member 10J. One end portion of an imagetransmission optical system 30 is also attached to the tip member 54Jwhen the above two halves are joined together. A prism 39 is providedbetween an inspection window 37 and an objective lens 38.

FIGS. 22 and 23 show a method of uniting optical fibers intermediateopposite ends thereof. As shown in FIG. 23, in its memorized shape, atubular member 10K used in this embodiment has a circular cross-section,and has a generally S-shaped axis. As shown in FIG. 22, the tubularmember 10K is processed in such a manner that it is larger in diameterand is curved along its axis more gently than its memorized shape. Anumber of optical fibers 20 are inserted through the tubular member 10K.At this time, the curvature or bending of the tubular member 10K in theaxial direction is gentle, and besides the cross-sectional area of areception space 11K is large, and therefore the insertion of the opticalfibers 20 is easy. Then, the tubular member 10K is heated to be returnedto its memorized shape, so that the tubular member 10K is reduced indiameter and is brought into the S-shaped, bent condition, therebyuniting the optical fibers 20 intermediate the opposite ends thereof.The opposite end portions of the optical fibers 20 are united in themanner as described above in any one of the above embodiments.

An optical fiber bundle 25K obtained by thus uniting the optical fibers20 is incorporated into an endoscope. An intermediate portion of theoptical fiber bundle 25K is received within a body 51K of the endoscope.The body 51K includes a base portion 51Ka, and a hollow projection 51Kbprojected from the base portion 51Ka. The above tubular member 10K isreceived in the base portion 51Ka and the projection 51Kb. The opticalfiber bundle 25K extended from the projection 51Kb is covered by a lightguide cable. The optical fiber bundle 25K is protected by the tubularmember 10K, and therefore is prevented from being damaged by movableportions in the body 51K.

In the embodiment shown in FIGS. 24 and 25, there are used an outertubular member 10K₁ of a transverse circular cross-section and an innertubular member 10K₂ of a transverse circular cross-section smaller indiameter than the outer tubular member 10K₁. The outer tubular member10K₁ is made of a shape memory alloy, and is processed in such a mannerthat it is larger in diameter than its memorized shape. The outertubular member 10K₁ has a through hole 12 for allowing the leakage of anadhesive. The inner tubular member 10K₂ is received in the outer tubularmember 10K₂ to form a reception space 11K therebetween, and one endportions of optical fibers 20 are inserted into the reception space 11K.At this time, the front ends of the optical fibers 20 are spacedrearwardly from one ends of the tubular members 10K₁ and 10K₂. Then, theouter tubular member 10K₁ is heated to be returned to its memorizedshape having the smaller diameter, thereby uniting the optical fibers20. Then, one end portion of an image transmission optical system 30including an objective lens is inserted into and fixed to the innertubular member 10K₂, and an annular glass pane 27K serving as anillumination window is fitted between the front end portions of thetubular members 10K₁ and 10K₂. A tip assembly thus obtained is fitted inand fixed to a through hole 54Ka in a tip member 54K.

The inner tubular member 10K₂ of FIG. 24 may be replaced by an innertubular member 10K₂ ' of FIG. 26. Instead of the outer tubular member10K₁, the inner tubular member 10K₂, 10K₂ ' may be made of a shapememory alloy. Alternatively, in addition to the outer tubular member10K₁, the inner tubular member 10K₂, 10K₂ ' may be made of a shapememory alloy. In these cases, the inner tubular member 10K₂, 10K₂ ' isprocessed in such a manner that it is smaller in diameter than itsmemorized shape, and when the inner tubular member is heated, it isreturned to its memorized shape having the larger diameter, therebyreducing the cross-sectional area of the reception space 11K. Instead ofthe outer tubular member 10K₁, the inner tubular member 10K₂ may have anadhesive leakage through hole. Alternatively, in addition to the outertubular member 10K₁, the inner tubular member 10K₂ may have an adhesiveleakage through hole.

In the embodiment shown in FIGS. 27 to 29, there are used a tubularmember 40 and a partition plate 45 of a shape memory alloy. As shown inFIG. 28, the partition plate 45 in its memorized shape is flat, and hasa width equal to the inner diameter of the tubular member 40. Thepartition plate 45 is processed in such a manner that it is curved intoan arcuate transverse cross-section at an ordinary temperature. Thecurved partition plate 45, when received into the tubular member 40,divides an internal space of the tubular member 40 into two sections,that is, a pair of reception spaces 41 and 42. One end portions ofoptical fibers 20 is inserted into the lower reception space 41 of alarger volume. Alternatively, the end portions of the optical fibers 20are first inserted into the tubular member 40, and then the partitionplate 45 is inserted into the tubular member 40 in such a manner thatthe partition plate 45 rests on the optical fibers 20 during theinsertion.

Then, the partition plate 45 is heated to be returned to its memorizedshape, that is, the flat shape. As a result, the partition plate 45 isdisposed on the center of the tubular member 40, and the cross-sectionalarea of the reception space 41 is reduced, thereby uniting the endportions of the optical fibers 20. Preferably, the central portion ofthe partition plate 45 is prevented by a jig from upward movement whenthe partition plate 45 is to be heated.

Then, a front end portion of an image transmission optical system 30 isinserted into and fixed to the other reception space 42. A tip assemblythus obtained is fitted in and fixed to a through hole 54La in a tipmember 54L.

The present invention is not limited to the above embodiments, andvarious modifications can be made. For example, the cross-sectional areaof the reception space may be reduced by returning the tubular memberfrom a transverse circular cross-section to a memorized, transversenon-circular cross-section by application of heat. Where there are useda pair of tubular members, and the inner tubular member is made of ashape memory alloy, the cross-sectional area of the reception space maybe reduced by returning the inner tubular member from a non-circularcross-section to a memorized, circular cross-section by application ofheat.

The united optical fibers may be used in the image transmission opticalsystem of the endoscope. The united optical fibers may also be used inother devices than an endoscope.

What is claimed is:
 1. A method of uniting a number of optical fiberscomprising the steps of:(a) preparing a tubular member of a shape memoryalloy with a reception space, wherein the tubular member has a bent axisin its memorized shape; (b) processing the tubular member in such amanner that the cross-sectional area of said reception space is largerthan the cross-sectional area in the memorized shape of said tubularmember and that said axis of the tubular member contains a gentler bendcompared with the bend of the bent axis in the memorized shape; (c)applying an adhesive to portions of a number of optical fibers over apredetermined length; (d) inserting said portions of said optical fibersinto said processed tubular member after steps (b) and (c); (e)subsequently heating said tubular member to return the tubular member tothe bend of the axis in memorized shape and to reduce thecross-sectional area of said reception space, thereby uniting saidoptical fibers received in said tubular member, a cross-sectional shapeof said united optical fibers being determined by said memorized shapeof said tubular member; and (f) curing said adhesive by said heating.